Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$83.75	4.622%	$87.6209	$87.62	$87.60	$87.60
Purchase #2	$96.31	9.401%	$105.3641	$105.36	$105.35	$105.40
Purchase #3	$151.76	7.779%	$163.5654	$163.57	$163.55	$163.60
Purchase #4	$225.87	8.753%	$245.6404	$245.64	$245.65	$245.60
Purchase #5	$43.34	5.204%	$45.5954	$45.60	$45.60	$45.60
Purchase #6	$243.35	13.356%	$275.8518	$275.85	$275.85	$275.90
Purchase #7	$84.64	13.520%	$96.0833	$96.08	$96.10	$96.10
7 purchase totals =	$929.02		$1,019.7213	$1,019.72	$1,019.70	$1,019.80